Mensuration is a division of mathematics that studies geometric figure calculation and its parameters such as area, length, volume, lateral surface area, surface area, etc. It outlines the principles of computation and discusses all the essential equations and properties of various geometric shapes and figures. Mensuration may refer to Measurement. Theory of Measurement, Mensuration (mathematics), a branch of mathematics that deals with the measurement of various parameters of geometric figures and many more. Forest mensuration is a branch of forestry that deals with measurements of the forest stand. Chapter 20 deals with the method of finding the perimeter and area of figures like rectangle, square and triangle. The perimeter of a closed plane figure is the length of its boundary. Area of a closed plane figure is the measure of the region (surface) enclosed by its boundary. In a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.